This invention relates to electrical interference shielding and, in particular, to a self-adhering electromagnetic interference seal for a door on a cabinet.
In systems such as telecommunications switching systems or computer systems, electromagnetic interference (EMI) can leak through the surface between a door and a cabinet frame of such a system. The prior art has attempted to prevent this leakage by using gaskets that are a flexible metal sheath woven around a foam or rubber type of core. These gaskets must be tucked into a channel around the periphery of the door in order to be installed correctly. Subsequent closing of the door then allows electrical contact to occur between the door and the cabinet frame via the gasket. Problems occur in inserting these gaskets into the channel around the door. Mechanical insertion of these gaskets must be correctly executed in order to obtain their optimal performance. This typically requires meticulous use of tools to properly and fully insert the gasket. Repetition of these insertion methods can lead to physical effects on the workers performing the methods such as carpal tunnel syndrome and sore fingers. In addition, such techniques are labor intensive, hence are expensive. Also, the repetitive opening and closing of the door can cause, over time, excessive wearing of the gasket and can degrade the performance of the gasket.
The foregoing problems are solved and a technical advance is achieved by an apparatus and method that uses a new compound to produce a magnetic tape having low electrical resistivity and high magnetic absorptivity. The magnetic tape self-adheres around a cabinet door opening such that when a cabinet door is closed, the magnetic tape provides an EMI seal with low electrical resistivity and high magnetic absorptivity. In addition, the magnetic tape electrically connects the door to the cabinet. To achieve greater EMI shielding, separate magnetic tape pieces can be positioned on both the cabinet and cabinet door. Advantageously, the compound is of a magnetically lossy Manganese-Zinc (soft ferrite material) having a complex permeability plus cobalt, nickel, or iron (ferromagnetic materials). The Manganese-Zinc material may advantageously be Product 3S1, 3C11, 3E25 or 3E27 manufactured by the Phillips Corporation of The Netherlands which is readily commercially available.